Caffeine Serum
Ingredients overview
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Key Ingredients
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The Inkey List Caffeine SerumIngredients explained
Propanediol is a natural alternative for the often used and often bad-mouthed propylene glycol. It's produced sustainably from corn sugar and it's Ecocert approved.
It's quite a multi-tasker: can be used to improve skin moisturization, as a solvent, to boost preservative efficacy or to influence the sensory properties of the end formula.
We don't have description for this ingredient yet.
A so-called fatty (the good, non-drying kind of) alcohol that does all kinds of things in a skincare product: it makes your skin feel smooth and nice (emollient), helps to thicken up products and also helps water and oil to blend (emulsifier). Can be derived from coconut or palm kernel oil.
This long-named, polymer molecule (big molecule from repeated subunits) is a helper ingredient that's good at emulsifying and stabilizing oils into water-based formulas. It also acts as a thickening and gelling agent that creates nice, non-sticky and supple textures. It works over a very wide pH range (3-12) and can be used to thicken up low-ph formulas, such as exfoliants. Its recommended used range is 0.3-3%.
Jojoba-derived emollient wax esters (fatty acid + fatty alcohol) that make your skin feel nice and smooth. Chemically speaking, pure jojoba oil is also a wax ester (read our shiny explanation here), however, the ingredients called jojoba esters on the ingredient lists are made from jojoba oil and/or hydrogenated jojoba oil via interesterification.
They have multiple versions with variable fatty acid chain length and the ingredient can have a liquid, a creamy, a soft or firm paste, or even a hard wax consistency. The common thing between all versions is, that unlike most normal triglyceride oils, jojoba esters have superior stability, provide non-greasy emolliency and are readily absorbed into the skin.
The combination of glycerin + two behenic acid molecules that works as an oil-gelling agent, emulsion stabilizer, and high-performance compacting agent in pressed powders. We wrote a bit more at its little sis, glyceryl behenate.
We don't have description for this ingredient yet.
It seems to us that squalane is in fashion and there is a reason for it. Chemically speaking, it is a saturated (no double bonds) hydrocarbon (a molecule consisting only of carbon and hydrogen), meaning that it's a nice and stable oily liquid with a long shelf life.
It occurs naturally in certain fish and plant oils (e.g. olive), and in the sebum (the oily stuff our skin produces) of the human skin. As f.c. puts it in his awesome blog post, squalane's main things are "emolliency, surface occlusion, and TEWL prevention all with extreme cosmetic elegance". In other words, it's a superb moisturizer that makes your skin nice and smooth, without being heavy or greasy.
Another advantage of squalane is that it is pretty much compatible with all skin types and skin conditions. It is excellent for acne-prone skin and safe to use even if you have fungi-related skin issues, like seborrhea or fungal acne.
The unsaturated (with double bonds) and hence less stable version of Squalane is Squalene, you can read about it here >>
Hello, our favorite molecule that helps us wake up in the morning and then keeps us going through the day. As a super well-known stimulant from coffee, tea and plenty of other soft drinks, Caffeine needs no introduction. So we will skip right to the part where we talk about what the hell it does in so-so many cosmetic products.
Looking at the research, we were surprised to find how versatile Caffeine is. It is a small, water-loving molecule with pretty good skin penetration abilties. Once in the skin, it has nice antioxidant properties, meaning that it reduces the formation of evil free radicals and it might even be useful in preventing UV-induced skin cancers.
A well-known thing about Caffeine is that it improves the microcirculation of the blood vessels. Though conventional wisdom and anecdotal evidence says that this property is helpful for dark under-eye circles and puffy eyes, we have to mention that the double-blind research we have found about a 3% caffeine gel concluded that "the overall efficacy of the selected caffeine gel in reducing puffy eyes was not significantly different from that of its gel base." But you know, the proof is in the pudding.
Another thing Caffeine is used for in body care products is its anti-cellulite effects. In theory, it can speed up the lipolysis process (the "fat burning" by our cells) and stimulate the draining lymph system that might lead to the improvement of cellulite. But here again, the evidence that it actually makes a measurable, let alone visible, improvement on actual human beings is limited (we could find only some animal skin studies or caffeine being combined with other actives).
Last, but not least, we have to write about caffeine and hair growth. The theory is that it can inhibit the activity of the 5-α-reductase enzyme that plays an important role in hair loss and allows a renewed growth phase of the hair. We have found some recent and promising research to back this up. A 2017 study compared a 0.2% caffeine liquid with a 5% Minoxidil (an FDA approved active to treat baldness) solution and found that "a caffeine-based topical liquid should be considered as not inferior to minoxidil 5% solution in men with androgenetic alopecia", or English translation means that the caffeine liquid was pretty much as good as the FDA-approved Minoxidil stuff. Not bad!
Overall, we think that caffeine is a very versatile and biologically active ingredient. Even though some of its effects are more hyped up than backed up, it is still a nice to have on many ingredient lists.
A type of lipid that's the major (about 75%) component of all cell membranes. As for skincare, it works as an emollient and skin-identical ingredient.
It has a water-loving head with two water-hating tails and this structure gives the molecule emulsifying properties. It is also often used to create liposomes, small spheres surrounded by phospholipid bi-layer designed to carry some active ingredient and help its absorption.
It's the triglyceride of behenic acid that works as a thickening or gelling agent, as a compacting agent for pressed powders, and improves heat stability of emulsions.
If you have spotted ethylhexylglycerin on the ingredient list, most probably you will see there also the current IT-preservative, phenoxyethanol. They are good friends because ethylhexylglycerin can boost the effectiveness of phenoxyethanol (and other preservatives) and as an added bonus it feels nice on the skin too.
Also, it's an effective deodorant and a medium spreading emollient.
It's one of the most commonly used thickeners and emulsion stabilizers. If the product is too runny, a little xanthan gum will make it more gel-like. Used alone, it can make the formula sticky and it is a good team player so it is usually combined with other thickeners and so-called rheology modifiers (helper ingredients that adjust the flow and thus the feel of the formula). The typical use level of Xantha Gum is below 1%, it is usually in the 0.1-0.5% range.
Btw, Xanthan gum is all natural, a chain of sugar molecules (polysaccharide) produced from individual sugar molecules (glucose and sucrose) via fermentation. It’s approved by Ecocert and also used in the food industry (E415).
We don't have description for this ingredient yet.
A common little helper ingredient that helps water and oil to mix together, aka emulsifier.
Super common little helper ingredient that helps products to remain nice and stable for a longer time. It does so by neutralizing the metal ions in the formula (that usually get into there from water) that would otherwise cause some not so nice changes.
It is typically used in tiny amounts, around 0.1% or less.
The combination of glycerin + behenic acid that comes either in a fine powder or waxy solid form. Together with the di- and triglyceride of behenic acid, the trio has remarkable gelling properties helping cosmetic chemists to create ultra-soft and non-tacky waterfree gels. They also have great emulsion stabilizing properties, and work as high-performance compacting agents for makeup products that come in the form of pressed powders.
It's also vegetable origin, and Ecocert certified.
Butylene glycol, or let’s just call it BG, is a multi-tasking colorless, syrupy liquid. It’s a great pick for creating a nice feeling product.
BG’s main job is usually to be a solvent for the other ingredients. Other tasks include helping the product to absorb faster and deeper into the skin (penetration enhancer), making the product spread nicely over the skin (slip agent), and attracting water (humectant) into the skin.
It’s an ingredient whose safety hasn’t been questioned so far by anyone (at least not that we know about). BG is approved by Ecocert and is also used enthusiastically in natural products. BTW, it’s also a food additive.
We don't have description for this ingredient yet.
It's an alternative, natural preservative that comes from radishes fermented with Leuconostoc kimchii, a lactic acid bacteria that has been used to make traditional Korean dish, kimchi. During the fermentation process, a peptide is secreted from the bacteria that has significant antimicrobial properties.
It is one of the more promising natural preservatives that can be used even alone (recommended at 2-4%), but it's not as effective as more common alternatives, like parabens or phenoxyethanol.
- It’s naturally in our skin and behaves there like a sponge
- It can bind up to 1000 times its own weight in water
- It is a big molecule from repeated subunits (polymer) so different molecular weight versions exist (unfortunately there is no way to determine MW from INCI list only)
- High-molecular-weight-HA (>500 kDa) is an excellent surface hydrator, skin protectant and can act as an osmotic pump helping water-soluble actives to penetrate deeper into the skin
- Low-molecular-weight-HA (< 500 kDa) can hydrate the skin somewhat deeper though it is still a big molecule and works mainly in the epidermis (outer layer of the skin)
- Low-molecular-weight-HA might also help the skin to repair itself by increasing its self-defense (~ 200kDa used in the study)
- Ultra-low-molecular-weight-HA (<50kDa) is a controversial ingredient and might work as a pro-inflammatory signal molecule
A big molecule created from repeated subunits (a polymer of acrylic acid) that magically converts a liquid into a nice gel formula. It usually has to be neutralized with a base (such as sodium hydroxide) for the thickening to occur and it creates viscous, clear gels that also feel nice and non-tacky on the skin. No wonder, it is a very popular and common ingredient. Typically used at 1% or less in most formulations.
We don't have description for this ingredient yet.
It's a common little helper ingredient that helps water and oil to mix together. Also, it can help to increase the solubility of some other ingredients in the formula.
A four amino acid peptide with the amino sequence of glycine-glutamine-proline-arginine. It is attached to palmitic acid (a fatty acid) to increase oil solubility and skin penetration.
It works by reducing the production of the signal molecule, interleukin-6 (IL-6) which promotes inflammation in the skin and less inflammation means slower degradation of important things (like collagen) that results in younger looking skin for a longer time.
It works in synergy with its pal, Palmitoyl Tripeptide-1 in the famous Matrixyl 3000 complex. You can read some more about the famous duo here.
A really famous peptide that is part of Matrixyl 3000, the most sold peptide complex in the word. Before we go and find out what the big deal with Matrixyl 3000 is, let's just focus on Palmitoyl Tripeptide-1 itself for a bit.
It's a small three amino acid (they are the building blocks of all proteins) peptide with the amino sequence of glycine-histidine-lysine, or GHK. GHK is attached to palmitic acid (a fatty acid) to increase oil solubility and skin penetration.
The GHK part is the important one as it's a type I collagen fragment. When collagen naturally breaks down in the skin, the resulting peptide fragments signal to the skin that it should get to work and create some nice, new collagen. Adding in collagen fragment peptides, like GHK, might trick the skin into thinking that collagen has broken down and it's time to create some more.
Therefore, Palmitoyl Tripeptide-1 is believed to be able to stimulate collagen production in the skin, and more collagen means fewer wrinkles and younger looking skin.
In Matrixyl 3000, Palmitoyl Tripeptide-1 is coupled with Palmitoyl Tetrapeptide-7 and the duo works in synergy to reduce wrinkles and give younger looking skin. According to the manufacturer's in-vivo (made on real people) test, applying 3% Matrixyl 3000 twice a day for 2 months resulted in all of the following things:
- 39.4% reduction in surface occupied by deep wrinkles
- 32.9% reduction in main wrinkle density
- 19.9% reduction in main wrinkle average depth
- 16% improvement in roughness
- 16.2% in lifting effect
- 5.5% improvement in elasticity
- 15.5% improvement in skin tone
Manufacturer results, of course, always have to be taken with a pinch of salt, but if you like peptides, the Matryxil 3000 duo is one of the best-proven and most well-known ones and it's something that is worth trying.
It’s pretty much the current IT-preservative. It’s safe and gentle, but even more importantly, it’s not a feared-by-everyone-mostly-without-scientific-reason paraben.
It’s not something new: it was introduced around 1950 and today it can be used up to 1% worldwide. It can be found in nature - in green tea - but the version used in cosmetics is synthetic.
Other than having a good safety profile and being quite gentle to the skin it has some other advantages too. It can be used in many types of formulations as it has great thermal stability (can be heated up to 85°C) and works on a wide range of pH levels (ph 3-10).
It’s often used together with ethylhexylglycerin as it nicely improves the preservative activity of phenoxyethanol.
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| what‑it‑does | solvent | moisturizer/humectant |
| what‑it‑does | emulsifying |
| what‑it‑does | emollient | viscosity controlling |
| irritancy, com. | 2, 2 |
| what‑it‑does | viscosity controlling |
| what‑it‑does | soothing | emollient | moisturizer/humectant |
| what‑it‑does | emollient |
| what‑it‑does | skin-identical ingredient | emollient |
| irritancy, com. | 0, 1 |
| what‑it‑does | antioxidant | perfuming |
| what‑it‑does | emulsifying |
| what‑it‑does | skin-identical ingredient | emollient |
| what‑it‑does | emollient |
| what‑it‑does | preservative |
| what‑it‑does | viscosity controlling |
| what‑it‑does | emulsifying | surfactant/cleansing |
| what‑it‑does | chelating |
| what‑it‑does | emollient | emulsifying |
| what‑it‑does | moisturizer/humectant | solvent |
| irritancy, com. | 0, 1 |
| what‑it‑does | emollient |
| what‑it‑does | antimicrobial/antibacterial | preservative |
| what‑it‑does | skin-identical ingredient | moisturizer/humectant |
| what‑it‑does | viscosity controlling |
| irritancy, com. | 0, 1 |
| what‑it‑does | emulsifying | surfactant/cleansing |
| irritancy, com. | 0, 0 |
| what‑it‑does | cell-communicating ingredient |
| what‑it‑does | cell-communicating ingredient |
| what‑it‑does | preservative |